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That’s not my drug – it’s too presumptive

Prosecutors must beware of “presumptive” analyses and that a “positive” may, in fact, be a “false positive”, writes Dr Brynn Hibbert, in collaboration with Unisearch.

Dr Brynn Hibbert, in collaboration with Unisearch • 06 December 2024

Whether your client is a top athlete with a banned steroid in their urine, or someone who is accused of making a prohibited drug in their garage chemistry lab, evidence against them will include chemical analysis, which identifies, and sometimes quantifies, the substance in question. Before going into all the reasons why that substance might have come into your client’s possession (think international swimmers and contaminated hotel food), it would be prudent to consider whether the analytical chemistry itself is right or admissible. As an academic chemist, I have been called as an expert witness for prosecution and defence in multiple cases for over 30 years. During that time, I have explained to courts how drugs are made and how we can detect them once imbibed.

In Australia, sports drugs are usually picked up in urine or blood tests by the state sports drug testing laboratory. For clan labs, when a drug is suspected to be present, a sample is taken and submitted to a state or federal drug analysis laboratory. It may be that the officers at the scene make a preliminary analysis using handheld devices that include, for example, a roadside saliva test, or a handheld infrared instrument. A positive result is noted, and a sample is sent for confirmatory analysis. The confirmatory test for sports or street drugs is done by professional analysts working in a laboratory that has accreditation to international standards (for example, ISO/IEC 17025:2017) for the test. In Australia, accreditation is bestowed by the National Association of Testing Authorities (NATA).

First point of call: check the lab’s accreditation

Check that the laboratory’s accreditation is current and for the alleged substance, keeping in mind that sports drug testing labs have been known to work when their accreditation has lapsed, which will implicate the test’s validity. However, it is unlikely that a laboratory with proper accreditation will be found to have made an error in identifying or quantifying a drug. I know of only one case – R v Piggott, Griffiths and Simeon, from the NSW Court of Criminal Appeal – in which an appeal court found that there was reasonable doubt about the identification of a drug made by an accredited laboratory. This was such an unusual case that I wrote an academic paper about it.

Beware of a “presumptive” analysis and that a “positive” may, in fact, be a “false positive”.

In the absence of analysis by an accredited laboratory, prosecutions can have a hard time. In a 2023 case, R v Snounou, where Border Force used handheld devices to identify a liquid precursor seized on entry to the country, the NSW District Court rejected the evidence. The judge accepted that the analysis undertaken by Border Force officers, while being compelling, was, by its own admission, “presumptive”. Giving expert evidence, I explained that a presumptive test is considered “sensitive” in that if presented with the actual target chemical, it will give a correct positive result with high probability, but that such a presumptive test is not necessarily “selective” because an apparently positive result might come from a very similar, but different, chemical (i.e. a false positive).

The drug, the whole drug, and everything but the drug

Even if the identity of the drug is not in doubt, there may still be questions to be asked about the quantity. A nice pile of pure white powder that can be weighed presents no great problem, but what about small amounts distributed over a clandestine laboratory or a bucket of something with only 1 per cent of the drug mixed in? The “admixture clause” in the Drug Misuse and Trafficking Act 1985 catches all mixtures without much room for manoeuvre, but there is some reluctance to invoke the clause when the mixture is clearly waste and the drug component is small.

In practical terms: assessing the validity of the scientific evidence presented.

So, when confronted with a client pleading innocence to a drug manufacture or sports drug charge, some useful areas to consider and question may include:

• Accreditation and assessment: Has the sampling been done correctly and sent to an accredited laboratory? This might be an issue with new drugs that are claimed analogues of prohibited substances.
• Chain of custody: What has been the drug’s chain of custody, and what variables may have impacted the substance?
• Quantification: Check quantification, especially when weights are near a border between trafficking/ indictable/ commercial/ large commercial.
• Client red flags: If the client is adamant that the alleged drug could not be present, subpoena the laboratory records, and have an expert check the analysis, including standards used and any calibration of instruments.
• Comparison: For sports drug samples, is there a “B” sample, and has that been stored, transported, and analysed correctly by way of comparison?

In conclusion, when confronted by very scientific-looking analytical evidence, it is worth remembering the words of Robert Burns: “There is no such uncertainty as a sure thing.”

Dr Brynn Hibbert AM FRSN is a Unisearch expert, an emeritus professor of analytical chemistry and honorary dean of emeriti, School of Chemistry, ̽��ϵ��.